Multiple control elements mediate activation of the murine and human interleukin 12 p40 promoters: Evidence of functional synergy between C/EBP and Rel proteins
Multiple control elements mediate activation of the murine and human interleukin 12 p40 promoters: Evidence of functional synergy between C/EBP and Rel proteins
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DOI：
10.1128/mcb.17.8.4572
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发表时间：
1997-08-01
影响因子：
5.3
通讯作者：
Smale, ST
中科院分区：
文献类型：
--
作者：
Plevy, SE;Gemberling, JHM;Smale, ST
白细胞介素12（IL-12）是一种异源二聚体细胞因子，其活性对于辅助性T细胞1应答至关重要。IL-12 p40亚基基因在细菌产物诱导后在巨噬细胞中表达，并且其表达通过γ干扰素增强。在这项研究中，我们进行了功能分析的小鼠和人类p40启动子在小鼠巨噬细胞系RAW 264.7。从小鼠p40启动子的转录强烈诱导的脂多糖和热杀死单核细胞增生李斯特菌（HKLM），但启动子活性没有增强γ干扰素。通过广泛的突变体分析，确定了参与激活转录的多个顺式作用元件。最关键的元件，其活性在小鼠和人类中是保守的，位于相对于鼠转录起始位点的位置-96和-88之间。该元件与先前描述的NF-κ B B半位点（其与Rel蛋白相互作用）具有功能协同作用，DNA酶I足迹法和电泳迁移率变动分析证明C/EBP蛋白与关键元件相互作用，但在核提取物中，未观察到C/EBP和Rel蛋白与其各自位点的协同结合。有趣的是，HKLM在放线菌酮的存在下诱导启动子活性，与翻译后机制的诱导一致。结果表明，C/EBP和Rel蛋白在细菌激活IL-12 p40转录中起重要作用。然而，许多复杂的相互作用将需要澄清，以充分了解p40的调控。
Interleukin 12 (IL-12) is a heterodimeric cytokine whose activity is critical for T-helper 1 responses. The gene for the IL-12 p40 subunit is expressed in macrophages following induction by bacterial products, and its expression is augmented by gamma interferon. In this study, we performed a functional analysis of the murine and human p40 promoters in the murine macrophage cell line RAW 264.7. Transcription from the murine p40 promoter was strongly induced by lipopolysaccharide and heat-killed Listeria monocytogenes (HKLM), but promoter activity was not enhanced by gamma interferon. Multiple cis-acting elements involved in activated transcription were identified through an extensive mutant analysis. The most critical element, whose activity is conserved in mice and humans, is located between positions -96 and -88 relative to the murine transcription start site. This element exhibits functional synergy with a previously described NF-kappa B half-site which interacts with Rel proteins, DNase I footprinting and electrophoretic mobility shift assays demonstrated that C/EBP proteins interact with the critical element, but in nuclear extracts, cooperative binding of C/EBP and Rel proteins to their respective sites was not observed. Interestingly, promoter activity was induced by HKLM in the presence of cycloheximide, consistent with induction by posttranslational mechanisms. The results suggest that C/EBP and Rel proteins play important roles in the activation of IL-12 p40 transcription by bacteria. However, many complex interactions will need to be clarified to fully understand p40 regulation.